Underwater pulse jet motor

ABSTRACT

An underwater pulse jet motor comprises a stator and, within the stator, a rotor which has axially extending ducts at its periphery. The stator includes a closing segment which closes off the forward ends of the ducts successively as they pass it during rotation of the rotor. Gas under pressure is injected into the ducts through an injection passage formed in the stator in alignment with the closing segment, injection openings in the ducts coming successively into register with the injection passage for this purpose. In order to form a buffer of water in each duct between the closing segment and the injection opening, the opening is disposed downstream of the upstream end of the duct, and an efficient seal against the escape of the gas between the upstream ends of the ducts and the closing segment is thus achieved. The buffer water can be arranged to flow at a restricted rate downstream into the central passage to provide an ejector effect to increase the water flow through the central passage at low forward speeds of the motor.

Waite tates Patent 1191 ,llarry [111, 3,872,665 [451 Mar. 25, 1975UNDERWATER PULSE JET MGTOR [75] Inventor: Philippe ,larry, Sevres,France [73} Assignee: Le Moteur Moderate, Boulogne Billancourt, France[22] Filed: Jan. 22, 1974 [21] Appl, No: 435,603

[30] Foreign Application Priority Data Feb. 9, 1973 France r. 73.04711[52] US. Cl 60/221, 60/227, 60/222 [51] 1nt.Cl B63h 11/02 [58] Field ofSearch 60/221, 222, 227; 115/16,

156] References Cited UNlTED STATES PATENTS 2,943,440 7/1960 Andras60/221 3269.1 12 8/1966 Kemenczky 3.271947 9/1966 Kemenczky 60/2213,492,820 2/1970 0/221 3,783,814 l/1974 Zovko .1 60/222 PrimaryEmminer-Clarence R. Gordon Armmcy. Agent, or Firm-Finnegan, Henderson,Farahow and Garrett [57] ABSTRACT An underwater pulse jet motorcomprises a stator and. within the stator, a rotor which has axiallyextending ducts at its periphery. The stator includes a closing segmentwhich closes off the forward ends of the ducts successively as they passit during rotation of the rotor. Gas under pressure is injected into theducts through an injection passage formed in the stator in alignmentwith the closing segment, injection openings in the ducts comingsuccessively into register with the injection passage for this purpose.In order to form a buffer of water in each duct between the closingsegment and the injection opening, the opening is disposed downstream ofthe upstream end of the duct, and an efficient seal against the escapeof the gas between the upstream ends of the ducts and the closingsegment is thus achieved. The buffer water can be arranged to flow at arestricted rate downstream into the central passage to provide anejector effect to increase the water flow through the central passage atlow forward speeds of the motor.

10 Claims, 9 Drawing Figures PATEHTEB MR 2 5 I975 sum-1 pr 3 III: I I I{1X1 {HT F MAR 2 5 iBTS sum 3 o 3 UNDERWATER PULSE JET MOTOR The presentinvention concerns an underwater pulse jet motor of the type comprisinga stator within which is mounted for rotation a rotor provided at itsperiphery with longitudinal ducts, each constituting a pulse jet unit,and a pressurized gas source for successively feeding the ducts of therotor through at least one fixed injection orifice formed in the statorand co-operating with a segment which is provided at the upstream end ofthe stator and which serves to close the ducts at their upstream ends.

Various forms of construction of pulse jet motors of this kind areknown. However, their industrial use has involved considerabledifficulties on account of the numerous technological problems, inparticular the problem of establishing a seal between the stator and therotor in the area where the closing segment is located. It is in factextremely difficult, if not impossible, to establish a good gas-tightseal in this zone, and the resulting losses can considerably reduce theperformance of the motor.

According to this invention there is provided an underwater pulse jetmotor comprising a stator, a rotor mounted for rotation within thestator and provided at its periphery with longitudinally extendingducts' fiaving open upstream and downstream ends, a closing segmentfixed with respect to the stator and closing off the upstream ends ofsaid ducts successively during rotation of the rotor, the statorproviding an injection orifice at the location of said segment, apressurised gas source for supplying pressurised gas to the injectionorifice, each of the ducts in the rotor having an injection aperturewhich comes into register with the said injection orifice when theupstream end of the said duct is closed off by the closing segment, saidinjection orifice and injection openings being disposed downstream ofthe upstream ends of the ducts whereby when the pressurised gasissupplied into the injection openings a buffer of pressurised water isformed between the closing segment and the injection openings.

It will be readily appreciated that as a result of this arrangement theproblem of establishing a seal in the zone of the closing segment isautomatically solved in that the pressurised gases injected into theducts of the rotor are isolated from said segment by a buffer of water.It is obviously much easier to establish a water-tight seal than agas-tight seal.

In one embodiment of the invention, ejector passages are formed in theclosing segment to place the upstream portion of each of the ducts ofthe rotor in communication with a central passage provided for the flowof water through the rotor, these ejector passages being directeddownstream at their ends adjoining the central passage. Thus, when thepressurised water forming the buffer escapes through the ejectorpassages in the closing segment, an ejector or siphon effect is achievedat the forward end of the rotor. This siphon effect causes water to bedrawn in at the upstream end of the central passage and thus enables therotor ducts to be filled when they pass out of alignment with theclosing segment. It will also be appreciated that with an arrangement ofthis kind the time required for filling the ducts with water isconsiderably reduced so that the motors performance is improved at lowforward speeds of displacement of the motor.

Some embodiments of the invention will now be described by way ofexample with reference to the annexed diagrammatic drawings in which:

FIG. 1 is a simplified longitudinal section through an underwater pulsejet motor in accordance with the invention,

FIG. 2 is a front elevation of the motor of FIG. 1,

FIG. 3 is a fragmentary sectional view illustrating a modification ofthe arrangement of FIGS. 1 and 2,

FIG. 4 is a fragmentary front view corresponding to FIG. 3, with someportions cut away,

FIG. 5 is a fragmentary sectional view illustrating a second embodimentof the invention,

FIG. 6 is a sectional view on line VIVI of FIG. 5,

FIG. 7 is a fragmentary sectional view illustrating a third embodimentof the invention,

FIG. 8 is a sectional view on the line VIII-VIII of FIG. 7, and

FIG. 9 illustrates a fourth embodiment of the invention.

The pulse jet motor illustrated in FIGS. 1 and 2 has a hollow stator 1having a profiled form suitable to enable it to move under water. Withinthe stator there is rotatably mounted, by means of roller bearings suchas that shown at 2, a hollow rotor 3. On its periphery the rotor isprovided with a series of longitudinal ducts 4 each constituting a pulsejet unit. These ducts extend along a part-helical path thus enabling therotor to rotate automatically without the need for providing additionaldriving means.

Formed in a supporting strut at the top of the stator l is a port 5connected to a pressurised gas source, not illustrated, which isdesigned to supply the gas to the ducts 4 of the rotor 3 in turn, andthe port cooperates with a closing segment 6 provided on the topupstream portion of the stator. This closing segment is designed to sealhermetically and successively the upstream ends of the ducts 4 so as toenable the water contained in the ducts to be expelled in the downstreamdirection under the action of the pressurised gas supplied through theport 5. It will also be seen that this closing segment, as shown in FIG.2, extends circumferentially over approximately four consecutive ducts.

The port 5 for supplying pressurised gas first communicates with anannular chamber 7 formed in the stator 1 around the upstream portion ofthe rotor 3. This annular chamber communicates with a fixed injectionorifice 8 which is disposed in the area where the closing segment 6 islocated and which is disposed axially downstream of the upstream end ofthe rotor 3. When the latter turns, the injection orifice 8 communicatesin turn with the ducts 4 of the rotor by way of an injection opening 9which is formed directly in each of these ducts and which comes intoregister with the injection orifice.

The mode of operation of a pulse jet motor will now be brieflydescribed.

The ducts 4 are filled with water in a dynamic man ner simply as aresult of the speed at which the pulse jet motor moves, and when one ofthese ducts is brought into communication with the pressurised gassource by way of its opening 9 when the latter moves into register withthe fixed injection orifice 8, the water in the duct is immediately andautomatically expelled downstream, since the duct in question is at thattime closed at the upstream end by the closing segment. Rotation oftherotor 3 is maintained by the reaction of the mass of water on thelateral walls of the helical ducts 4, and thus ensures that the pulsejet motor operates continuously without the need for any other source ofpower.

Since the injection orifice 8 is disposed axially downstream of theupstream ends of the ducts 4, a buffer 10 of pressurised water is formedupstream when pressurised gas is injected into the duct in question;this buffer is delimited by the opening 9 of the duct and by the closingsegment 6. The pressurised gas in the duct is thus isolated from theclosing segment by a certain mass of water which ensures theestablishment of a good seal in this zone. It will be appreciated thatit is considerably easier to obtain a good watertight seal than a goodgas-tight seal. Consequently the risk of leakage of gas at the closingsegment is eliminated, and the performance of the pulse jet motor isthus improved accordingly.

It will also be appreciated that the pressurised water of the buffer 10,formed in this way in the upstream portion of each of the ducts 4 of therotor, can be used for various purposes. FIGS. 3 and 4 illustrate one ofthese possibilities. A number of passages 11, three for example, areformed in the closing segment 6 for establishing communication betweenthe upstream ends of the aligned ducts 4 and the ambient water. Theouter ends of these passages are directed both towards the centre of themotor and downstream thereof.

Consequently, when the pressurised water of the buffer l escapes throughthe passages 11, it sets up an axial siphon effect which causes water tobe drawn into the inlet end of the motor. This action facilitates thefilling of the ducts of the rotor with water at the fixed point, andreduces the time for filling these ducts at slow speeds of travel of themotor. The passages 11 can, with advantage, be inclined sideways in thesame direction as that in which the rotor rotates, as illustrated inFIG. 4, so as to increase further the siphon effect set up.

In the embodiment illustrated in FIGS. and 6, passages 12 are formeddirectly in the inner wall of the rotor 3 in the upstream portion ofeach of the ducts 4. These passages 12 are directed downstream, and theyare all also inclined in a common direction in relation to the radialdirection, as illustrated in FIG. 6, so as not to intersect on the axisof rotation of the rotor 3. Ejection of the pressurised water of thebuffer through these inclined passages thus creates at the inlet to themotor an axial and rotary siphon effect in the direction opposite tothat in which the rotor turns. This siphon effect obviously causes waterto be drawn in, in the manner previously described, but because of itscentrifugal action it also enables the speed of rotation of the rotor 3to be regulated with precision. For this purpose a suitably ratedcentrifugal valve can be advantageously provided in each ofthe passages12. It will also be appreciated that the particular arrangement justdescribed can be used in conjunction with that illustrated in FIGS. 3and 4.

It is obviously possible also to create a siphon effect in thedownstream portion of the pulse jet with a view to obtaining uniformvelocity distribution in the outlet plane and thus increasing thepropelling power of the motor. The velocity at which water is ejectedfrom the ducts of the rotor is always greater than the speed of travelof the pulse jet. It then suffices to establish connection between thishigh-velocity water and the water of low velocity of the surroundingarea, for the purpose of achieving a siphon effect.

For this purpose and as illustrated in FIGS. 7 and 8, the rotor 3 ishollow over a certain portion of its length at its downstream end so asto connect the ducts 4 with the central passage of the motor. An innerplate 13, fixedly connected to the stator 1 by two webs 14 is howeverprovided to close the cut away portion of the ducts in the Zone wherepressurised gas is injected. Thus, the siphon effect only takes placebeyond said plate, that is to say where the velocity at which water isejected is at its highest, whereas the greatest possible inertia of thecolumn of water is maintained when injection occurs. This downstreamsiphon effect can of course be used in conjunction with the upstreamsiphon effect obtained with the aid of the arrangements illustrated inFIGS. 3 and 4, or 5 and 6.

Finally, FIG. 9 illustrates a third possible use of the pressurisedwater of the buffer 10 in the case where the pressurised gas source isconstituted by a superheated steam generator. It will be appreciatedthat the use of superheated steam offers particular advantages in thepowering of an underwater pulse jet motor. In particular the cycle maybe an open one, the pulse jet performing the function ofa condenser.Furthermore, since the superheated steam is condensible it disappearsafter ejection and this means that there is no wake. Finally, the steamgenerator is a fairly quiet unit in which combustion is continuous andtherefore does not cause much pollution.

FIG. 9 shows aboiler 15 with a pipe coil 16, a burner 17 and afume-exhaust duct 18. The pipe coil 16 runs into a steam accumulator 19connected to the duct 5 for passing the steam into the annular chamber 7of the stator 1. Part of the steam produced is also collected through apipe system 20 for the purpose of actuating a pump 21 for supplyingwater to the boiler, this steam being discharged into the atmospherethrough a pipe 22.

The pump 21 is supplied directly with pressurised water from the buffer10 formed in each of the ducts 4 of the rotor when the superheated steamis injected. For this purpose, the pump is connected by a passage 23 toa pressurised water collector 24 which is formed in the upstream portionof the stator 1 and which is in communication with the upstream ends ofthe ducts 4 at the location of the closing segment 6. Thus, the pump 21is supplied with water already at a certain pressure and thereforeoperates at a reduced pressure differential with regard to the vapourpressure required for supplying to the ducts of the pulse jet units.Consequently, this pump can be of lower power than normally, and it cantherefore also be less costly.

It will be appreciated that all the particular arrangements that havebeen described can be used not only in the case of pulse jet motorscomprising a hollow rotor as illustrated in the annexed drawings, butcan also be used in the case of central-feed pulse jet motors disposedwithin an exterior hull.

I claim:

1. An underwater pulse jet motor comprising a stator, a rotor mountedfor rotation within the stator and provided at its periphery withlongitudinally extending ducts having open upstream and downstream ends,a closing segment fixed with respect to the stator and closing off theupstream ends of said ducts successively during rotation of the rotor, astator providing an injection orifice at the location of said segment, apressurised gas source for supplying pressurised gas to the injectionorifice, each of the ducts in the rotor having an injection aperturewhich comes into register with the said injection orifice when theupstream end of the said duct is closed off by the closing segment, saidinjection orifice and injection openings being disposed downstream ofthe upstream ends of the ducts whereby when the pressurised gas issupplied into the injection openings a buffer of pressurised water isformed between the closing segment and the injection openings.

2.. A motor as claimed in claim 1, wherein the rotor is annular toprovide a central passage open for the flow of water therethrough, atleast one ejector passage being provided for placing the locationbetween the closing segment and the injection openings of each duct incommunication with said central passage, at least when the injectionorifice registers with the injection opening of the said duct, the endof said ejector passage which opens to the central passage beingdirected in a downstream direction.

3. A motor as claimed in claim 2, wherein a plurality of said ejectorpassages are formed in the closing segment.

4. A motor as claimed in claim 3, wherein said downstream ends of theejector passages are directed at an angle to a direction radially of therotor.

5. A motor as claimed in claim 2, wherein the rotor is formed with aplurality of said ejector passages one in each of said ducts.

6. A motor as claimed in claim 5, wherein said downstream ends of theejector passages are all directed at a common angle to a directionradially of the rotor.

7. A motor as claimed in claim 1, wherein the rotor is annular andprovides a central passage therethrough. the rotor having radially innerand outer walls which define the radially inner and outer boundaries ofthe ducts, the downstream end portions of said inner wall being cutaway.

8. A motor as claimed in claim 7, wherein the stator provides a fixedpart-annular wall in the downstream end portion of said central passage,said part-annular wall being aligned axially with said inner wall of therotor and aligned circumferentially with the closing segment, and theupstream end of the part-annular wall being disposed adjacent thedownstream end of the inner wall.

9. A motor as claimed in claim 1, wherein said pressurised gas sourcecomprises a generator of superheated steam.

10. A motor as claimed in claim 9, further comprising a feed pumpconnected to supply water to said generator, and a passage which isformed in the closing seg ment and through which water from the upstreamends of the ducts can be fed to the pump.

1. An underwater pulse jet motor comprising a stator, a rotor mountedfor rotation within the stator and provided at its periphery withlongitudinally extending ducts having open upstream and downstream ends,a closing segment fixed with respect to the stator and closing off theupstream ends of said ducts successively during rotation of the rotor, astator providing an injection orifice at the location of said segment, apressurised gas source for supplying pressurised gas to the injectionorifice, each of the ducts in the rotor having an injection aperturewhich comes into register with the said injection orifice when theupstream end of the said duct is closed off by the closing segment, saidinjection orifice and injection openings being disposed downstream ofthe upstream ends of the ducts whereby when the pressurised gas issupplied into the injection openings a buffer of pressurised water isformed between the closing segment and the injection openings.
 2. Amotor as claimed in claim 1, wherein the rotor is annular to provide acentraL passage open for the flow of water therethrough, at least oneejector passage being provided for placing the location between theclosing segment and the injection openings of each duct in communicationwith said central passage, at least when the injection orifice registerswith the injection opening of the said duct, the end of said ejectorpassage which opens to the central passage being directed in adownstream direction.
 3. A motor as claimed in claim 2, wherein aplurality of said ejector passages are formed in the closing segment. 4.A motor as claimed in claim 3, wherein said downstream ends of theejector passages are directed at an angle to a direction radially of therotor.
 5. A motor as claimed in claim 2, wherein the rotor is formedwith a plurality of said ejector passages one in each of said ducts. 6.A motor as claimed in claim 5, wherein said downstream ends of theejector passages are all directed at a common angle to a directionradially of the rotor.
 7. A motor as claimed in claim 1, wherein therotor is annular and provides a central passage therethrough, the rotorhaving radially inner and outer walls which define the radially innerand outer boundaries of the ducts, the downstream end portions of saidinner wall being cut away.
 8. A motor as claimed in claim 7, wherein thestator provides a fixed part-annular wall in the downstream end portionof said central passage, said part-annular wall being aligned axiallywith said inner wall of the rotor and aligned circumferentially with theclosing segment, and the upstream end of the part-annular wall beingdisposed adjacent the downstream end of the inner wall.
 9. A motor asclaimed in claim 1, wherein said pressurised gas source comprises agenerator of superheated steam.
 10. A motor as claimed in claim 9,further comprising a feed pump connected to supply water to saidgenerator, and a passage which is formed in the closing segment andthrough which water from the upstream ends of the ducts can be fed tothe pump.